Commonly Misdiagnosed Conditions: Why Getting the Right Diagnosis Takes Time

Diagnostic errors are more common than most patients realize. A 2023 report from the Agency for Healthcare Research and Quality estimated that roughly 7.4 million emergency department visits in the United States each year involve a diagnostic error, contributing to between 371,000 and 1.1 million patient harms. While many conditions are straightforward to diagnose, others are notorious for being missed, delayed, or confused with something else.

Understanding which conditions are frequently misdiagnosed can help you recognize when to seek a second opinion and how to communicate more effectively with your healthcare team.

Conditions with High Misdiagnosis Rates

Endometriosis

Endometriosis affects roughly 10% of women of reproductive age, yet the average time from symptom onset to diagnosis is seven to ten years. The condition, in which tissue similar to the uterine lining grows outside the uterus, causes chronic pelvic pain, painful periods, and sometimes infertility. It is frequently dismissed as "normal period pain" or misdiagnosed as irritable bowel syndrome, pelvic inflammatory disease, or ovarian cysts.

The delay is partly due to the fact that definitive diagnosis historically required laparoscopic surgery, a step many physicians and patients are reluctant to take. Newer imaging techniques, including specialized transvaginal ultrasound and MRI, can now detect some forms of endometriosis without surgery, but awareness remains low among some primary care providers.

Celiac Disease

Celiac disease, an autoimmune condition triggered by gluten, is estimated to affect about 1% of the population. But studies suggest that up to 83% of people with celiac disease are undiagnosed or misdiagnosed. The condition was long believed to present primarily as digestive symptoms in children, but it is now understood to affect adults of all ages and can cause fatigue, anemia, bone loss, neurological symptoms, and skin rashes without any gastrointestinal complaints.

Common misdiagnoses include irritable bowel syndrome, chronic fatigue syndrome, and anemia of unclear cause. Screening involves a simple blood test (tissue transglutaminase IgA antibody), which is relatively inexpensive and widely available. Confirmation requires a small bowel biopsy.

Thyroid Disorders

Both hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid) produce symptoms that overlap with many other conditions. Hypothyroidism can cause fatigue, weight gain, depression, constipation, and cold intolerance, all of which can be attributed to aging, stress, or other medical conditions. Hyperthyroidism can mimic anxiety disorders, producing palpitations, tremor, weight loss, and insomnia.

Thyroid disorders are particularly underdiagnosed in older adults, where symptoms are often attributed to normal aging. A TSH (thyroid-stimulating hormone) blood test can detect most thyroid disorders and should be considered when symptoms are persistent and unexplained.

Lupus

Systemic lupus erythematosus (SLE) is an autoimmune disease that can affect virtually every organ system. Its symptoms, including fatigue, joint pain, skin rashes, and intermittent fevers, fluctuate over time and overlap with dozens of other conditions. The average time to diagnosis is approximately six years. Lupus is sometimes called "the great imitator" because it mimics so many other diseases.

Lupus disproportionately affects women, particularly women of color. Diagnosis requires a combination of clinical findings and laboratory tests, including antinuclear antibody (ANA) testing. A positive ANA alone is not diagnostic, as it can be found in up to 15% of healthy women.

Pulmonary Embolism

A pulmonary embolism (PE), a blood clot that travels to the lungs, is one of the most commonly missed diagnoses in the emergency department. Symptoms can be nonspecific: shortness of breath, chest pain, rapid heart rate, and, in some cases, cough or leg swelling. These symptoms overlap with pneumonia, asthma, anxiety, and musculoskeletal pain.

A 2019 study in the journal Diagnosis found that PE was one of the top three conditions involved in diagnostic errors leading to serious harm or death in the ED. The key to catching a PE is maintaining a high index of suspicion, especially in patients with risk factors such as recent surgery, prolonged immobility, cancer, hormone use, or a history of blood clots.

Why Misdiagnoses Happen

Several systemic factors contribute to diagnostic errors:

• Time pressure. Primary care visits average 15 to 20 minutes. This limited time makes it difficult to explore complex or unusual presentations.
• Cognitive biases. Anchoring bias (fixating on the first diagnosis that comes to mind) and availability bias (overweighting diagnoses seen recently) are well-documented in medical decision-making.
• Atypical presentations. Many conditions present differently based on age, sex, race, and comorbidities. Textbook presentations are often the exception rather than the rule.
• Fragmented care. When patients see multiple specialists without a coordinating provider, important connections between symptoms can be missed.

What You Can Do

Patients are increasingly recognized as important partners in the diagnostic process. Steps you can take include:

• Keep a written record of your symptoms, including when they started, what makes them better or worse, and how they affect your daily life.
• Ask your doctor: "What else could this be?" This simple question encourages broader diagnostic thinking.
• If your symptoms are not improving with treatment, go back. Lack of response to a treatment can be an important diagnostic clue.
• Seek a second opinion if you feel your concerns are not being taken seriously, particularly for chronic symptoms without a clear explanation.
• Request copies of your test results and medical records. Having your own records makes it easier to get a fresh perspective from another provider.